This project is directed at refining, adapting, and developing technologies for purposes of supporting morphologically based research. It is primarily technology development rather than exclusively hypothesis based research and has application to research throughout DIR. Our aim is to make the technology serve research - and not to engage in technology driven activities. We serve as an intellectual resource for NIEHS investigators and only perform technical tasks as full research collaborators. Examples of recent efforts include: (1) development of image analysis procedures for epidermal carcinogenesis studies, (2) establishing methods for estimating the number of hepatocytes in the livers of rodents treated with different xenobiotics, (3) development and application of easier techniques for identifying cells in different phases of the cell cycle and for quantitating these, (4) stereological measurement of preneoplastic lesions as predictors of in archival tissue specimens, (6) development of computer assisted image analysis to quantitate BrdU stained S- phase cells, (7) establishing utility of administration of BrdU in drinking water in lieu of using osmotic minipumps. Histochemical methods currently being developed or used for support include: p16, ERR alpha1, PDGF alpha & beta, CYP2J2, insulin, glucogon, somatostatin, WT-1, ER, PgR, IGF-I, bcl-3, KAI-1, BrdU, PCNA, and P53.